Environmental magnetic properties used to assess sediment sources and transport patterns in the muddy area along the Zhejiang coast, China

The muddy area along the Zhejiang coast contains a record of historical environmental conditions and can facilitate a better understanding of the linkages among terrestrial sediment fluxes, littoral sediment dynamics, and climate change. However, the origin and transport of the sediments in this muddy area has been open to debate. We present a detailed environmental magnetic study with high-density sampling to provide magnetic evidence for the input and transport of the materials in this region. Our results show that magnetic minerals in the sediments are generally dominated by magnetite and titanomagnetite with minor amounts of maghemite and hematite. The magnetic minerals are mainly pseudo-single domain (PSD) particles, and decrease in concentration seawards. Based on the coastal current flow and magnetic characteristics, we argue that the sediments in this area are mainly derived from the Changjiang River, the mountainous rivers in the surrounding islands, and erosion by coastal currents. Notably, the increase in sediment input from small mountainous rivers and coastal erosion in the Zhejiang coastal area is primarily associated with decreased sediment discharge from the Changjiang River. However, there is no evidence of the accumulation of Taiwan-derived sediment in this area.